For a complete rundown of testing equipment and procedures, please refer to the
article SPCR's Revised PSU Testing System. It is a close simulation of a
moderate airflow mid-tower PC optimized for low noise.

The W0029 in the SPCR PSU Test Rig.

In the test rig, the ambient temperature of the PSU varies proportionately with
its actual output load, which is exactly the way it is in a real PC
environment. But there is the added benefit of a precise high power load tester
which allows incremental load testing all the way to full power for any
non-industrial PC power supply. Both fan noise and voltage are measured at
various loads. It is, in general, a very demanding test, as the operating
ambient temperature of the PSU often reaches 40°C or more at full power.
This is impossible to achieve with an open test bench setup.

Great effort has been made to devise as realistic an operating environment
for the PSU as possible, but the thermal and noise results obtained here still
cannot be considered absolute. There are far to many variables in PCs and far
too many possible combinations of components for any single test environment
to provide infallible results. And there is always the bugaboo of sample variance.
These results are akin to a resume, a few detailed photographs, and some short
sound bites of someone you've never met. You'll probably get a reasonably good
overall impression of that person, but it is not quite the same as an extended
meeting in person.

Ambient conditions during testing were 23°C and 20 dBA, with input of 120 VAC
/ 60 Hz measured at the AC outlet.

Thermaltake Fanless Purepower 350
Model W0029 - 350W TEST RESULTS

DC Output (W)

65

90

150

200

250

300

max*

AC Input (W)

88

116

190

250

310

358

334*

Efficiency

74%

78%

79%

80%

81%

84%

n/a*

Intake Temp (°C)

31

32

35

39

41

43

44

PSU Exhaust (°C)**

43

46

55

62

69

77

79

Noise (dBA/1m)

n/a

electric buzz

n/a

n/a

buzz - 23

buzz - 23

-

Power Factor

0.63

0.64

0.66

0.67

0.67

0.67

n/a

NOTE: The ambient room temperature during testing varies
a few degrees from review to review. Please take this into account when
comparing PSU test data.* Failed to deliver the 350W maximum rated power. See text.
** The temp sensor was wedged between two of the external fins.

ANALYSIS

The sample worked mostly without any noise at lower power loads. There was a bit of buzzing (6~700 Hz) at some loads, but it was modest, somewhat dependent on the precise mix of loads on the various lines, and not audible from more than a couple foot away. The buzzing got louder at >250W output, and in an otherwise quiet system, it might get loud to be an annoyance.

Full rated power could not be reached. The unit exhibited current overload when asked to deliver 350W, with the load set precisely to the maximum for each voltage line. The PSU did not power down, however. Whether the reduced AC current draw is an indication of current clamping is not clear; the few PSUs I've managed to overload by trying to draw too much power have shut down outright. With this kind of reduced output behavior, the PC demanding such power from this PSU would most likely crash or exhibit some other serious instability.

The PSU was left at the maximum power load for less than ~5 minutes. There was no point to making it burn.

1. VOLTAGE REGULATION stayed within published parameters up to the 300W load. The low and high voltages seen on each of the main lines are shown:

+12V: 11.7 to 12.2

+5V: 4.7 to 5.1

+3.3V: 3.2 to 3.3

When the 350W load was dialed in, voltages fell significantly below their norms:

+12V: 10.25V

+5V: 4.2V

+3.3V: 3.1V

2. EFFICIENCY was very good. In fact, given the possible 2-3 year old circuit being used here, the efficiency figures we obtained are downright amazing. It made us double check our results with two different power meters. For most of the range in which this power
supply is likely to be used, efficiency remained between 74~81%. The 84% efficiency reached at 300W is excellent, although by this time, the buzzing noise probably makes the unit less useful.

3. POWER FACTOR was typical for a unit without PF correction, with a range
between 0.63~0.67, increasing with power output.

4. COOLING: A cursory glance at the "intake" and external PSU heatsink temperature rows in the test result table is enough to tell us that the heatpipes and copper fins work as intended. They wick the heat efficiently from the hottest portions of the PSU out to the copper fins. It doesn't tell us how well the copper fins "sink" the heat into the air. Given the high temps, perhaps not well enough. Admittedly, we lack the resources to full analyze the meaning of these temps. Suffice it to say that during several days of testing, the PSU never shut down even when the fin temperature approached 80°C.

CONCLUSIONS

The Thermaltake Fanless Purepower 350 model W0029 is an interesting power supply. It has high efficiency and seems to work well in the power range of interest to most quiet PC users. It's silent at low power. There is some buzzing noise that can get intrusive at high power levels, but it's unlikely that this PSU would be used in a system that calls for such power for any length of time.

The unit does not offer PCIe video card support, nor does it come with a 24-pin ATX main connector, which is best for PCIe boards. SLI is not even a consideration with its modest power output capability.

The 350W rating is obviously not right. 300W is the realistic maximum power capability of this unit.

The cooling system appears to work well, but ultimately, whether the design provides good enough cooling for its internal components can only be judged by widespread use over time. The lack of compliance with the ATX12V v2.0 Design Guide is disappointing, especially given the price.

Ultimately, we're going to sit on the fence dithering and say we're not sure that we recommend it. We're more comfortable with a Silverstone or Antec Phantom fanless PSU. This Thermaltake would probably work well in a low power (<150W DC) minimalist system for a user who understands thermal issues around fanless PSUs. For more general users, it's not as safe a choice.

* * *

Much thanks to Thermaltake for the opportunity to examine this power supply.